This invention relates to quantum non-locality modulated signalling methods.
It has been demonstrated, by Aspect and others, that under some circumstances, certain atomic species and non-linear downconversion crystals can be induced to emit pairs of photons that have correlated polarizations, depending on the nature of the source, the correlated linear polarizations of the photon pairs are either always at 90 degrees to each other or always parallel to each other. The photons can be provided in separate streams, with either one of each pair in each stream or with each photon having an equal probability of being found in either stream. It has further been strongly demonstrated that, under certain conditions, these photons are not emitted with any predetermined directions of linear polarization, but that the polarization states of the photons is only fixed upon measurement of the polarization of one of the photons. Thus, assuming perpendicular polarization correlation, if the one photon is measured to be vertically polarized, then the other photon becomes horizontally polarized at that moment, no matter how far apart the two photons have traveled prior to the measurement. The polarization states of the two photons are 100 percent entangled; measurement of the polarization state of one photon determines the polarization state of the other, but prior to measurement, their polarization states are indeterminate. In essence, the two photons are parts of the same object; no matter how far they travel apart from each other, changing the properties of one photon instantly changes the properties of the whole object, including the properties of the other photon. The experiments of Aspect, et al., have convinced most quantum theorists that the polarizations of these correlated photons are non-local; the polarizations are not predetermined at the time of emission, but are rather condensed into a particular state at the moment of "observation" of one of them. A. Aspect, P. Grangier and G. Roger, Phys. Lett. 47, 460 (1981) and 49, 91 (1982). A. Aspect, J. Dalibard and G. Roger, Phys. Lett. 49, 1804 (1982); Z. Y. Ou and L. Mandel, Phys. Lett. 61, 50 (1988) and 61, 54 (1988).
Various quantum theorists and experimentalists have addressed the question of whether the non-locality effects of correlated particles can be employed as the basis for sending information. The published conclusions of Aspect and others have asserted that such is not possible. Baggott, Jim, The Meaning of Quantum Theory, Oxford Science Publications, Oxford University Press, 1992, pp. 148-150; P. Eberhardt and R. Ross, Found. Phys. Lett., 2, 127 (1989). The logic is that the passage rate of either stream of correlated photons through its respective polarizer will always appear random. What is not random is the correlation of polarization between the two photons. Since the receiver cannot know the state of the sender's photon, then the receiver cannot glean information from the photons he receives. The signal and the noise are, therefore, of equal magnitude.
These conclusions are correct, so far as they go. In the systems which have been previously analyzed, the correlated photon light source is placed midway between the sender and the receiver and a single polarizer is considered at each end of the dual photon stream, one for the sender and one for the receiver, and the coincidence of photon detection at the sender and receiver, as a function of polarizer angle, is observed. It does appear to be true that information cannot be sent by correlation of photon polarizations by means of such an apparatus designed especially for coincidence counting.
It appears that prior researchers in this field have assumed that since information cannot be transmitted by polarization correlation using two polarizers and two or more detectors, then the addition of more polarizers to the system will not improve matters. It is apparently also generally assumed that once a photon passes through a linear polarizer its polarization state is fixed.
I have discovered that additional polarizers, when properly arranged and controlled, allow the separation of signal information from noise in a correlated photon system and enable the use of such a system for the transmission of information. This end is achieved without the need to perform correlation measurements. Unlike previous correlated quantum particle communication methods the subject invention does not require that both photons of a correlated pair be sent to the receiver so that coincidence counts may be performed. In fact, if polarization correlation measurements or coincidence count measurements are performed, the correlation may appear to be random. Furthermore, it is therefore not the state of the photon, or quantum object, correlation which is communicated, but rather the state of the apparatus which is communicated. The apparatus is considered to include the system at the sending end, the system at the receiving end, and the correlated stream of photons which connect the two. A change in the apparatus at the sending end immediately affects the observations at the receiving end since the two ends are connected by single quantum objects with ends in both locations.